The present invention relates to a bulb-form lamp and a manufacturing method of a lamp case, and more particular, to a bulb-form lamp, which is constructed in a manner that a threaded portion of a lamp cap for making an electrical connection with a lighting circuit of the bulb-form lamp is formed out of a conductive resin.
For example, as a conventional bulb-form lamp, there is a compact self-ballasted fluorescent lamp. The compact self-ballasted fluorescent lamp is constructed in the following manner. More specifically, as shown in FIG. 13, an envelope 91 comprises a glass glove 11 and a lamp case 25. Further, an arc tube 10, a printed circuit board 13 on which a lighting circuit 14, and two lead wires 15a and 15b connected to the lighting circuit 14 so as to supply a power are received in the envelope 91.
A lamp cap 5 is screwed onto one end portion of the lamp case 25 so that the lamp case 25 is prevented from loosening by caulking or the like. The lamp cap 5 comprises a metal shell 5c forming a threaded portion 53, and an eyelet 5a fixed by pouring an eyelet glass 5b functioning as an insulator into the distal end portion of the metal shell 5c. The metal shell 5c and the eyelet 5a are integrated with each other. These metal shell 5c and eyelet 5a constitute an electrode for supplying a power to the lighting circuit 14.
The eyelet 5a consists mainly of Ni (nickel) plating brass. One lead wire 15a is let from a central hole 52 of the eyelet 5a to the outside, and then, is connected to the outer surface of the eyelet 5a by soldering. In this case, although is not shown, there is the case where the lead wire 15a and the eyelet 5a are connected by plasma arc welding using no solder in the light of environmental protection.
On the other hand, the metal shell 5c consists of metal such as Ni plating brass, aluminum or the like. The other lead wire 15b is led from the rear end portion of the metal shell 5c to the outside, and then, is connected to the outer surface of the metal shell 5c by soldering. In this case, although is not shown, there is the case where the lead wire 15b and the metal shell 5c are connected by resistance welding or TIG welding in the light of environmental protection.
The following is a description on a manufacturing method of the conventional bulb-form lamp as described above.
First, an arc tube 10 is assembled to a holder 12, and thereafter, is fixed by a silicon bonding agent or the like. A printed circuit board 13 is fixed with respect to the holder 12 fixing the arc tube 10 on the side opposite to the mounted arc tube 10. Thereafter, the lamp case 25 is fitted into the holder 12 mounting the arc tube 10 and the printed circuit board 13. A silicon bonding agent or the like is filled into a circular-arc gap formed at a portion where the lamp case 25 is fitted into the holder 12, and subsequently, the glove 11 is inserted and fixed into the circular-arc gap filled with the bonding agent. Then, the silicon bonding agent filled into the circular-arc or the like is dried and hardened in a high temperature furnace, and thereby, the lamp case 25 and the glove 11 is fully assembled with respect to the holder 12.
Next, the lamp cap 5 is screwed into the distal end portion of the lamp case 25, and subsequently, the lamp case 25 is fixed by caulking. In the case of assembling the lamp cap 5 to the lamp case 25, the lead wire 15a is led out of the central hole 52 of the eyelet 5a while the lead wire 15b is led out of the proximal portion of the metal shell 5c. 
Thereafter, the led-out portion of the lead wire 15b is connected to the outside of the metal shell 5c by soldering or resistance welding and TIG welding. Likewise, the lead wire 15a led out of the central hole 52 of the eyelet 5a is connected to the outside of the eyelet 5a by soldering or plasma arc welding.
In the manner as described above, the bulb-form lamp shown in FIG. 13 is completed.
By the way, in the above conventional bulb-form lamp, the lamp case 25 is independently molded out of a resin, and the lamp cap 5 is manufactured by an exclusive maker in a manner that the eyelet 5a and the metal shell 5c are fixed by the eyelet glass 5b. For this reason, in order to assemble the lamp cap 5 into the lamp case 25, the following various processes must be carried out; more specifically, when manufacturing the bulb-form lamp, the lamp cap 5 is inserted and screwed into the lamp case 25, and thereafter, is fixed by caulking. As a result, many working processes (man-hour) are required.
Further, when screwing the lamp cap 5, in the case where the threaded portion 53 of the metal shell 5c is strongly griped by an automatic machine, there is a possibility that the threaded portion 53 is deformed, and the eyelet glass 5b breaks or cracks.
Furthermore, in the case where caulking with respect to the lamp cap 5 is insufficient, the lamp cap 5 looses and comes off; conversely, in the case where caulking is too strong, there is a possibility that the lamp case 25 is broken. For this reason, it is difficult to control a caulking strength.
The present invention has been made in view of the above problems. It is, therefore, an object of the present invention to provide a bulb-form case, which can simplify an assembly of the bulb-form case so as to reduce an assembly cost, and has a high quality, and to provide a manufacturing method of a lamp case.
In order to solve the above problem, the present invention provides the following technical means. More specifically, according to one aspect, the present invention provides a bulb-form lamp comprising: an arc tube; a lighting circuit for lighting the arc tube; a lamp case receiving the lighting circuit; and a lamp cap mounted outside the lamp case and functioning as an electrode of the lighting circuit, a threaded portion of the lamp cap, that is, a shell being made of a conductive resin.
According to the present invention, the conductive resin shell functions as an electrode for supplying a power to the lighting circuit like the conventional metal shell. Moreover, in general, the conductive resin has a hardness lower than metal; therefore, it is possible to improve a combined strength in which the conductive resin shell is engaged with a male-threaded portion of socket when using the bulb-form lamp.
In the technical means of the present invention, the conductive resin shell is a composite part, which is molded integrally with the lamp case. By doing so, there is no need of carrying out processes for inserting the lamp cap into the lamp case, screwing, and caulking when assembling the bulb-form lamp like the conventional case. Therefore, it is possible to prevent a deformation of threaded portion by the assembling work, and no problem arises such that caulking is insufficient with respect to the lamp cap; for this reason, the lamp cap looses and comes off.
In the technical means of the present invention, the conductive resin shell and an eyelet constituting a distal portion of the lamp cap are composite parts, which are molded integrally with the lamp case. The resin portion of the lamp case is extended to an eyelet glass insulator of the conventional lamp cap, and thereby, there is no need of using the eyelet glass. Therefore, no problem arises such that the eyelet glass cracks like the conventional case.
In the technical means of the present invention, a part of the conductive resin shell is provided with a terminal connective portion projecting into the lamp case, and the terminal connective portion is connected with the lighting circuit so that the conductive resin shell and the lighting circuit are electrically connected. The lighting circuit is assembled to the lamp case so as to be connected with the terminal connective portion of the conductive resin shell, and thereby, the conductive resin shell and the lighting circuit are electrically connected. By doing so, the lead wire has no need to be soldered like the conventional case; therefore, there is no connection failure caused when the solder comes off in the shell portion.
In the technical means of the present invention, the terminal connective portion is connected with an electrode terminal led out of a printed circuit board of the lighting circuit. The terminal connective portion and the electrode terminal are connected, and thereby, it is possible to securely make an electrical connection of the conductive resin shell with the lighting circuit.
In the technical means of the present invention, a part of metal terminal buried in the conductive resin shell is exposed in the lamp case, and the part of metal terminal is connected with the lighting circuit so that the conductive resin shell and the lighting circuit are electrically connected. The lighting circuit is assembled to the lamp case so as to be connected to a part of the metal terminal buried in the conductive resin shell, and thereby, the conductive resin shell and the lighting circuit are electrically connected; therefore, the electrical connection between these can be securely made.
In the technical means of the present invention, a metal eyelet constituting a distal portion of the lamp cap may be fitted into a through hole formed at the lamp case distal portion. In this case, a process for assembling the eyelet to the lamp case is required; however, the same effect as above can be obtained.
Further, according to another aspect, the present invention provides a manufacturing method of a lamp case receiving a lighting circuit for lighting an arc tube of bulb-form lamp and having a lamp cap functioning as an electrode of the lighting circuit and mounted outside the lamp case, comprising the following steps of:
a primary process; and
a secondary process,
the primary process including the steps of:
closing a first cavity mold, which is formed along an outer profile of the lamp case and is provided with a protrusion at a shell of being a threaded portion of the lamp cap, and a core mold, which is formed along an inner profile of the lamp case and is provided with a recess portion capable of inserting the protrusion;
forming a cylindrical cavity along the profile of the lamp case;
injecting a molten resin into the cylindrical cavity; and
forming a primary molding, which is formed with a hole leading electrode by the protrusion, the secondary process including the steps of:
opening the dies;
fitting a second cavity mold provided with a threaded cylinder forming surface into the core mold holding the primary molding;
forming a threaded cylinder cavity including the hole leading electrode at an outer peripheral surface of the shell; and
injecting a molten conductive resin into the threaded cylinder cavity so that a part of the conductive resin is molded integrally with a shell, which is provided with a terminal connective portion projected into the lamp case, via the hole.
According to the present invention, the above primary and secondary processes are carried out, and thereby, the lamp case molded integrally with the shell is obtained; therefore, there is no need of carrying out a process for assembling the lamp cap to the lamp case like the conventional case. Moreover, the lighting circuit is assembled to the lamp case so as to be connected to the terminal connective portion of the conductive resin shell, and thereby, the conductive resin shell and the lighting circuit are electrically connected; therefore, the assembly of the lighting circuit can be readily made.
Furthermore, according to another aspect, the present invention provides a manufacturing method of a lamp case receiving a lighting circuit for lighting an arc tube of bulb-form lamp and having a lamp cap functioning as an electrode of the lighting circuit and mounted outside the lamp case, comprising the following steps of:
a primary process;
a terminal insertion process; and
a secondary process,
the primary process including the steps of:
closing a first cavity mold, which is formed along an outer profile of the lamp case and is provided with a protrusion at a shell of being a threaded portion of the lamp cap, and a core mold, which is formed along an inner profile of the lamp case and is provided with a recess portion capable of inserting the protrusion;
forming a cylindrical cavity along the profile of the lamp case;
injecting a molten resin into the cylindrical cavity; and
forming a primary molding which is formed with an electrode leading hole by the protrusion,
the terminal insertion process including the steps of:
opening the dies; and
inserting a metal terminal into the electrode leading hole of the primary molding so that the metal terminal is inserted and fixed into a recess portion of the core mold,
the secondary process including the steps of:
fitting a second cavity mold provided with a threaded cylinder forming surface into the core mold holding the primary molding;
forming a threaded cylinder cavity including a part of the metal terminal at an outer peripheral surface of the shell;
injecting a molten conductive resin into the threaded cylinder cavity so that a part of the metal terminal is molded integrally with a shell, which is provided with a terminal connective portion projected into the lamp case, via the electrode leading hole.
According to the present invention, likewise, there is no need of carrying out a process for assembling the lamp cap to the lamp case. Moreover, the lighting circuit is assembled to the lamp case so as to be connected to the metal terminal of the conductive resin shell, and thereby, the conductive resin shell and the lighting circuit are electrically connected; therefore, the assembly of the lighting circuit can be readily made.
In the technical means of the present invention, the primary process further includes a step of forming a through hole capable of fitting an eyelet constituting the distal portion of the lamp cap therein at the distal portion of the primary molding, and forming a recess portion for preventing the eyelet from coming off at the surroundings of the through hole. There is no need of forming the portion for mounting the eyelet by using an eyelet glass; therefore, the number of processes can be reduced.
In the technical means of the present invention, the primary and secondary processes are carried out by a two color molding process.
As described above, according to the present invention, the eyelet of the lamp cap and the conductive resin shell are molded integrally with the lamp case, and thereby, there is no possibility that the lamp cap looses and comes out of the lamp case. Moreover, when manufacturing the bulb-form lamp, there is no need of processes for inserting the lamp cap into the conventional lamp case, and fixing it by caulking. Therefore, it is possible to greatly reduce the number of assembling processes, and to reduce the assembly cost for the bulb-form lamp. Further, no problem arises such that the shell is deformed by caulking and the eyelet glass cracks; therefore, it is possible to manufacture a bulb-form lamp having a high quality.